Printing



Aug. 31, 1965 L. c. mou. 3,203,054

PRINTING Filed Deo. 11. 1961 y wi/MVM United States Patent O 3,203,054 ERlNTlNG Leslie Clarence Nicoll, lil Birchwood Road, Petts Wood, rpington, Kent, England Filed Dec. il, 1961, Ser. No. 153,502 Claims priority, application Great Britain, Oct. 24, 1956, 32,423/56; lan. 20, 196i, 2,375/61 1 Claim. (Cl. 22--S.5)

This application is a continuation-impart of my application iiled September 27, 1957, Serial No. 686,666, now abandoned.

The invention relates to stereo printing, and is more particularly concerned with the production of the stereo from the matrix.

In the customary method of production of the stereo, the matrix from which the stereo is cast is made from papier-mache, known as flong, and, after the pepiermache matrix has been taken by pressing from the forme, it is necessary to build up, i.e. pack the recesses in the back by sticking on paper strips until a substantially backed and liush surface is obtained which is suitable for insertion into the casting box, the backing ensuring that undesirable impressions do not occur in the iinished stereo. This backing of the stereo is tedious and slow, and the object of the invention is to obtain the same result in a quicker and more efficacious manner.

According to the invention, a stereo matrix consists of an impressed ilong backed by a sheet of material which has been applied during the making of the impression on the ong by the forme.

In particular the matrix accordingr to the invention is comprised in a thin, iiexible composite, porous plate having on one side printing impressions and on the opposite side a liat surface without depressions arising from the formation of the printing impressions, said plate being composed from two librous paper laminations namely a flong to receive the printing impressions and a single layer porous backing made from a paper having the character of uncompressed and uncalendered lilter paper compacted to a thin tlexible sheet and pre-impregnated with a non-phenolic stiffening and adhesive agent, the laminations in the composition of said plate being assembled loosely together with the tlong wet and the backing dry, said composite plate having had the fibres of the laminations thereof expanded into intermingling relation, wetted by the agent, compressed and adhesively bound together by heat and pressure applied to said assembly during the operation of making the printing impressions.

The heat and pressure referred to is applied by inserting the assembly between the platens of the normal matrix press and then operating the press, so as to consolidate the backing with the ong while the impression from the impression producing forme is being made on the flong.

During the pressing operation-which is of a duration and at temperatures and pressures corresponding to normal for matrix making--the backing becomes intimately incorporated with the ilong and lls up all the recesses which would otherwise occur between the complementary impressions in the back of the long made by the forme, and leaves a smooth, dat surface yon the outside. The further advantage of this backing over packing by strip backing applied after the matrix is made according to usual practice, is that itextends all over the matrix, lilling up all the recesses between the complementary impressions.

The thickness of the backing sheet should be of the order or" the depth of the recesses-referred to herein as the white area recesses-made normally on the reverse side of the ong by the type forme, the thickness thus being such that when the composite matrix is extracted ice from the press the projection of the backing surface in relation to the conventional backed iiong is negligible. Virtually the composite matrix is thus of a thickness corresponding to the normal unbacked matrix and can be dealt with in the ordinary way when producing the stereo therefrom.

The invention will be further described with convenient reference to the accompanying diagrammatic drawings (not to scale), in which:

FIGUREl l shows a cross-section of a typical laminated assembly of the invention (not t-o scale and somewhat enlarged) as applied to the matrix press,

FIGURE 2 is a cross-section of a typical composite stereo matrix made in accordance with the invention,

FIGURE 3 shows a conventional matrix made from a single tiong sheet and having `a build-up of paper strips adhesively applied on the back side thereof in the recesses corresponding to the white areas which will be hereinafter particularly described, and

FIGURE 4 shows the blowing up effect in the making of a matrix in accordance with the invention.

A practical form of backing material which is used for making the composite stereo matrix according to the invention, consists of a material known as Free-Flow lilter paper of approximately 0.050 inch thick, uncompressed and not calendered. It is impregnated with a stiifeniug and adhesive agent made from a solution of starch and potassium or ammonium dichromate in the proportion of live percent by weight dichromate to starch. The use of starch alone has had successful results, but the tanning action of the dichromate under the influence of heat and moisture arising in the matrix press operation has improved the backing, making the matrix more moisture resistant. The impregnated backing material after drying retains substantially its original thickness, but may be from 15 to 25 percent heavier; it also forms a comparatively rrn, but compressible, exible and porous board.

While the starch solution has generally been most economical and efficient, avoiding any tendency for the backing to stick t-o metal during the pressing operation, good results have been obtained with a weak solution of gelatine tanned with a dichromate.

To ensure the best results in the use of the backing, a perforated steam release plate (or plates) is (or are) inserted between backing sheet and the adjacent platen of the press.

In order that the features of the new matrix may be readily understood, reference will be first made to FIG- URE 3 which shows a conventional matrix made from a single flong sheet which is a thin librous paper product having a thickness which may vary between 0.018 to 0.030 inch. The casting surface 10 has been made by pressing the dampened flong between the platens such as P of the usual matrix press (FIGURE l) with the impression lor type forme 1 in position. As a result the liong has on its casting surface, printing impressions cousisting of intaglio recesses il and intervening relief elements 12. On the back, i.e. the reverse side of the ilong matrix, there are recesses 13 which are formed immediately under the relief elements l2. In the use of this matrix to cast a stereo therefrom, the relief elements 12 produce, in the stereo, recesses which are known as white areas since they come between the printing areas formed in relief on the stereo by the intaglio recesses 11 of the matrix. The recesses 13 in the matrix coming immediately under the relief elements 12 on the casting surface 10, are referred to herein as the white area recesses. They are usually about 0.050 inch deep, and if not iilled in, they leave the matrix weak at these points so that it sags or deforma thereat during the casting of the stereo to cause on the latter unwanted impressions.

To overcome this difficulty the conventional matrix has separate backing strips 14 adhesively stuck on in the white area recesses l after the matrix has been pressed, thereby finishing the matrix so as to make it ready for casting the stereo. The overall thickness of a finished conventional matrix may be in the order of 0.06 to 0.065 inch.

The process of sticking on these backing strips 14 is obviated by the present invention which incorporates a complementary backing with the flong when printing impressions are being pressed thereinto. This produces a thin flexible composite porous matrix plate with the reverse side fiat and smooth and entirely free of any unwanted impressions resulting from the forme used in the press, the overall thickness of this composite matrix being very little, if at all, greater than the overall thickness of the conventional backed matrix of FIGURE 3; thus the extra thickness of the composite matrix plate may be no more than in the order of 0.005 inch.

To produce this novel composite matrix plate, the process of the invention uses a lamination assembly which from FGURE 1 it will be seen consists of the forme l, the flong 2, the aforesaid backing 3, a wire mesh sheet 4, and a rigid perforated plate 5. The number of perforations 6 in the plate 5 are sufficient to allow the steam to escape during the pressing operation between the platens P of the matrix press indicated by dotted lines in the drawing, while the wire mesh sheet 4 (which is copper or other material not readily affected by steam) allows escape of steam but prevents the impressions of the perforations 6 in the plate 5 from making any significant marks on the finished exterior surface of the flat surface 9 of the finished composite matrix plate. In some cases the perforated plate may be dispensed with if the press platen is perforated.

After the assembly has been hot pressed between the platens P, it is removed from the press after opening the platens, and the plates l, 4 and S are separated from the composite matrix plate composed of fiong and backing as shown in FIGURE 2. This composite matrix plate comprises the impressed flong por-tion 2a (the impressions-intaglio recesses 1l and relief portions 1.2- being on the casting surface 7) having its fibres intermingled with the fibres of the backing portion 3a in such a manner that the reverse side of the matrix is a flat surface 9 and the demarcation between the portions is a wavy line 14a, with the result that the backing is thinner as at 15 beneath the intaglio recesses ll and is blown up into thicker humps 16 under the relief impression portions 12, which humps r16 in effect, lfill in all the white area recesses 1 3 (FIGURE 3) which would otherwise be formed in the back of the iiong as explained in connection with FGURE 3. The thickness of this novel composite matrix plate will usually approach within a thickness tolerance of 0.005 inch to the thickness of the conventional matrix of FIGURE 3. It thus can be used in exactly the same way in the casting of the stereos therefrom. To fulfill the requirements of the invention, the thickness of the backing 3 in the lamination assembly is such that the backing is thin and flexible, being in the order of depth of the usual white area recesses 13, and not less than such depth; for this purpose a thickness of about 0.050 inch is found to be satisfactory with a tolerance of 0.010 either way applicable.

It will be observed that the backing not only has a fibrous structure not unlike that of the ong, but its thin and flexible character makes it compatible with the iiong in all essential respects. In this respect it is quite different from the thick moulding blanketof the order of a quarter of inch of thickness-which has sometimes been used with a flong and stuck on to the back thereof before pressing. The intention of such thick moulding blankets is to reinforce the aforesaid white area recesses, but experience has shown that this does not result and the unwanted depressions occur in the stereo cast from such a matrix.

One of the novel and distinctive features of the composite matrix plate of the invention is its production by the application to a ilong in a loose (ie. not in any way adhered thereto) manner, of a paper backing which is a dry, flat, compacted but flexible lamination of appropriate thickness to fill the aforesaid White area recesses occurring in a conventional flong. This backing lamination is so pre-impregnated by the stiffening and adhesive agent that when placed dry and loosely together with the flong-which is wetted as normal-as a sandwich in the press, the effect of the backing under the heat and pressure of the press, first supports the flong while it collapses under the press, and then fiows and blows up into the white area hollows f3 of the flong arising from the type impressions, until at the end of the pressing operation the humps 16 reinforce the underside of the relief portions 12 and the whole sandwich has consolidated into one integral thin plate with the type impressions (1l, l2) on the flong side and a fiat surface 9 on the reverse side, with a thickness and flexibility for all practical purposes the same as a conventional flong made by normal processes and illustrated in FGURE 3.

Agents such as formaldehyde or thermosetting resin which preclude the softening and blowing up and flowing of the fibres of the backing into the fibres of the flong during the pressing process, have no application in the present invention, but the agent employed must be such that during the heat and pressure under the press it causes the backing material to become integrated with the reverse of the flong without the use of separate adhesive layers in the sandwich formation prior to the pressing.

The paper backing must be compatible with that of the ong to enable the blowing up and integration effect to be achieved, and for this purpose the backing is made from the aforesaid material having the character of uncompressed and uncalendered filter paper known as Free Flow filter paper, which is compacted to a thickness of approximately 0.050 inch, which is of the order of thickness of the depth of the white area recesses 13 (FGURE 3).

A suitable agent for impregnation of the backing consists of 30 gms. starch (Amylum), 11/2 gms. potassium or ammonium dichromate, and 11/2 litres of water, which is suficient to impregnate 15 square feet of .048 inch of the aforesaid Free Flow filter paper. impregnation is effected by passing the Free Flow lter paper through a vat of the impregnating solution and then over rollers into a heated drying chamber.

The pre-stilfening afforded by impregnation of the backing with the aforesaid agent is such that when dry the backing has flexibility and absence of brittleness which enables it to be handled and laid dry upon the wet ong when the wet-dry sandwich formation is to be formed for application to the press.

The invention requires that in the process of pressing the flong is first wetted, as in the normal pressing process, without the fbacking, and then the wet fiong and the dry backing are placed loosely together as a sandwich which, for best results, has laid over the backing side a wire mesh sheet and a drilled plate before insertion in the press, with the fiong side applied flat against the type forme as described with reference to FIGURE 1 of the drawing.

In the pressing operation-which usually lasts for about ten mniutes-the effects which take place may be explained as follows: the backing 3 acts in the initial pressure stage of a few seconds as a moulding blanket supporting the flong Z so that the material of the soft wetted flong is forced by the pressure into the depressions of the type forme l. As the pressure continues, the steam and heat loosen the fibrous structure of the backing-which acts as a reservoir of the stiffening agentso that it expands (what is herein called blowing up), flows into the white area recesses 13 and on to the high spots of the type pressing, and by continuing pressure the stiffening agent is forced into the fiong material, whereby the intermingled fibres of flong and backing (as indicated by 17 in FIGURE 4) are thoroughly wetted so as to be consolidated and united into a solidified, thin, at porous plate which is flexible and generally suitable for handling and bending to whatever shape is necessary for casting purposes. This composite plate (2a, 3a) is the matrix, and has type impressions (11, 12) on the front (flong) side and a flat surface on the reverse side. After it is taken from the press in a hot state, the composite matrix plate (2a, 3a) is set aside to cool before being placed in the casting box.

In general it has been found that .a stereotype matrix in accordance with the invention, can be made in about fifteen minutes, from assembly of the wet-dry sandwich to the dried cool matrix ready for the casting box.

As compared with other forms of matrix, the improved matrix has the characteristic of being able to stand up to high stereo-casting temperatures of 300 degrees centigrade without warping or disintegration, and thus has a considerable life in the order of thirty to forty casts.

It has been recognised in the trade that in the making of stereotype matrices, if a flong is made thick enough prior to pressing, there need be virtually no hollows at the back f the matrix which require support by an applied backing, but a thick flong resul-ts in a thi-ck matrix, which is normally unacceptable for casting since it tends to warp on drying after pressing--and also in the casting box-and it takes substantially longer to dry before it is usable in the casting box. The thin, flexible, porous matrix, according to the invention, avoids all these disadvantages.

A typical matrix, according to the invention, made in about fifteen minutes to a finished thickness of about 65 thousandths of an inch-which is of the order of the finished thickness of a usual matrix without the integral backing of the invention-has the following steps in the process of its manufacture (with further reference to FIGURE 1):

(l) Metal type or other forms 1 (after cleaning) are set up in the usual manner on a metal work table plate.

(2) On this set up a piece of thin fiong material 2 of standard form is laid in a damp state, having previously been soaked in a bath of water for about a minute.

(3) `On top of this damp fiong 2 a piece of backing material 3 as herein characterised in a dry state is placed so as to cover the whole surface of the flong.

(4) On top of the backing is applied in the following order a wire mesh sheet 4, a perforated steam release plate 5, and preferably a soft blanket, for example of news- 50 paper, indicated by dotted line B, in order to absorb the steam. After use, these can be dried and used again.

6 The whole sandwich assembly of 1 to 4 is then placed between the platens of a moulding press and subjected to the heat and pressure thereof for about ten minutes. 5 (6) At the end of the pressing period the press is opened, the assembly is withdrawn, and the hot finished matrix is separated from the type form, the elements of 4 being then set aside to cool. After a few minutes the composite matrix sheet is ready for use in the casting box, wherein it can be mounted fiat or bent to a curved shape as required.

(7) The use of a starch and dichromate stiffening agent has been found to have the advantage that the dichromate tans the starch colloid to render it moisture resistant, and apart from its iiowing and adhesive bonding effects in the integration of flong and backing during pressing, it does not cause the backing material to stick to the metal 0r perforated steam release sheet, and thus the need for pretreatment of the latter by black lead or other anti-stick material-which cannot be avoided in known matrix making processes where damp pressing is used-is unnecessary.

I claim:

A matrix for casting stereos, comprising a thin, fiexible, composite, porous plate having on one side printing impressions and on the opposite side a flat surface without depressions arising from the formation 0f the printing impressions, said plate including two compressed fibrous paper laminations namely a flong sheet having the printing impressions and a single layer porous backing of paper having the character of uncompressed and uncalendered filter paper compacted to a thin liexible sheet approximately 0.050 inch thick and pre-impregnated with a stifiening and adhesive agent consisting `of starch tanned `with a dichromate in the proportion of 5% by weight dichromate to starch, said composite plate having the fibers of the laminations thereof expanded into intermingling relation, compressed `and adhcsively bound together.

References Cited by the Examiner UNITED STATES PATENTS DAVID KLEIN, Primary Examiner.

WILLIAM B. PENN, Examiner. 

